1. Field of the Invention
The present invention relates to a substrate treatment apparatus, and more particularly, to a substrate treatment apparatus having uniform plasma.
2. Discussion of the Related Art
In general, a semiconductor device, a display device or a thin film solar cell is fabricated through a deposition process for depositing a thin film on a substrate, a photolithography process for exposing or covering a selected area of the thin film using a photosensitive material, and an etching process for patterning the selected area of the thin film. Among the processes, the deposition process and the etching process are performed in a substrate treatment apparatus, which is set up with optimum conditions.
FIG. 1 is a cross-sectional view of illustrating a substrate treatment apparatus according to the related art, and FIG. 2 is a schematic view of illustrating a substrate treatment apparatus including a transfer chamber according to the related art.
In FIG. 1, a substrate treatment apparatus 10 includes a process chamber 12, a backing plate 14, a gas supply line 36, a gas distribution plate 18, a substrate holder 22, a substrate entrance 40, and an outlet 24. The process chamber 12 provides a reaction space. The backing plate 14 is located in an upper portion inside the process chamber 12 and is used as a plasma electrode. The gas supply line 36 is connected to the backing plate 14 and provides source gases into the process chamber 12. The gas distribution plate 18 is located under the backing plate 14 and is formed of aluminum. The gas distribution plate 18 includes a plurality of injection holes. The substrate holder 22 is used as a counter electrode to the plasma electrode, and a substrate 20 is disposed on the substrate holder 22. The substrate 20 is carried into or out of the process chamber 12 through the substrate entrance 40. Reaction gases used in the process chamber 12 and by-products are discharged through the outlet 24.
The gas supply line 36 is connected to a radio frequency (RF) power source 30 through a power feeding line 38. In addition, the gas supply line 36 is connected to a remote plasma controller 50. A matcher 32 for adjusting impedance is set up between the RF power source 30 and the power feeding line 38. A buffer space 26 is formed between the gas distribution plate 18 and the backing plate 14, and the gas distribution plate 18 is put on a support 28 extending from and connected to the backing plate 14. The source gases are supplied into the process chamber 12, and an RF power from the RF power source 30 is applied to the backing plate 14 and the gas distribution plate 18. Plasma is generated due to an electric field between the gas distribution plate 18 and the substrate holder 22. Therefore, a thin film is formed on the substrate 20, or a thin film on the substrate 20 is etched.
The gas distribution plate 36 is positioned at a central part of the backing plate 14 corresponding to a center of the process chamber 12. The backing plate 14 has a symmetric structure with respect to each of a vertical line and a horizontal line passing through the gas supply line 36. To process the substrate 20 in the process chamber 12, as shown in FIG. 2, a slot valve 42 is connected to the substrate entrance 40 of the process chamber 12, and a transfer chamber 44 is connected to the slot valve 42. The transfer chamber 44 supplies the substrate 20 to the process chamber 12 or carries the substrate 20 out of the process chamber 12.
The slot valve 42 and the transfer chamber 44 are sequentially connected to a first side of the process chamber 12 having the substrate entrance 40, but a slot valve and a transfer chamber are not connected to a second side of the process chamber 12 opposite to the substrate entrance 40. In addition, when the RF power is applied to the backing plate 14 and the gas distribution plate 18, RF currents provided from the RF power source 30 flow along surfaces of the process chamber 12, the slot valve 42 and the transfer chamber 44, which are formed of conductive materials. In addition to the backing plate 14 and the gas distribution plate 18, the RF currents are carried to surfaces of adjacent conductors, that is, the process chamber 12, the slot valve 42 and the transfer chamber 44.
By the way, in the related art substrate treatment apparatus 10 as shown in FIG. 1 and FIG. 2, the plasma may not be uniformly generated. Therefore, a thin film having a non-uniform thickness may be formed on the substrate 20. The non-uniform thickness of the thin film may result from asymmetry of the electric field. The RF currents at the second side of the process chamber 12 opposite to the substrate entrance 40 flow only along the surface of the process chamber 12 and have a first path. On the other hand, the RF currents at the first side of the process chamber 12 having the substrate entrance 40 flow along the surfaces of the process chamber 12, the slot valve 40 and the transfer chamber 44 and has a second path, which is longer than the first path due to the slot valve 40 and the transfer chamber 44.
Accordingly, the asymmetry of the electric field is caused by difference between the first and second paths. The asymmetry of the electric field disturbs generation of uniform plasma and affects formation of a thin film. A thickness of the thin film formed on the substrate 10 adjacent to the first side of the process chamber 12 is thicker than a thickness of the thin film formed on the substrate 10 adjacent to the second side of the process chamber 12. Therefore, the thickness of the thin film is not uniform.
To solve the problem, the uniformity of the plasma may be improved by increasing a distance between the gas distribution plate 18 and the substrate holder 22. However, in this case, a density of plasma is lowered, and a density of a thin film formed on the substrate 10 is lowered.